A、Two centuries. B、300 years ago. C、In 1691. D、In the 16th century. B本题考查考生对事件发生时间的掌握。文中两处提供了本题的答案，在文章的开始和结尾，我们可以听到以上所列关键词，故B正确。

The first postal service in North America began in New  England (33)in the 17th century. All mail arriving in Massachusetts colony was sent to the home of appointed official in Boston.  In turn, he would deliver the mail from Boston  on horseback to its destination, receiving one penny for each  good article of mail. Later in the century postal services  were established between Philadelphia and Delaware. (34) In 1691,  the British crown appointed the first postmaster  general to have charge of the mail for all the colonies in  North America. Later,  Benjamin Franklin served as the  postmaster general for the British government and then was  made postmaster by the newly formed United States govern ment. (35)Franklin was responsible for establishing the United States’postal systems on a permanent basis. He in creased the number of post office,  introduced the use of  stagecoaches to carry mail, and started a package service system. They were used  to carry mail into the towns. Some communities, especially  those out west, were far from the services of transportation. To serve them, the post office developed a system called "star routes". Private contractors paid to deliver mail to the  communities from railways by horse and wagon. The postal service, which was (32) started over 3 centuries ago, has developed into an extensive government service with post offices in every city, town, and village in the United States.